Two types of transcriptional controls on polyphosphate kinase (PPK) gene promoters in different bacteria
Abstract
In bacteria, polyphosphate kinase (PPK) is responsible for the synthesis of polyP from ATP and the reversible conversion of polyP and ADP to ATP. PPK plays a crucial role in the ability of bacteria to adapt to nutritional stringencies and environmental stresses. Bacterial ppk gene expression was tested at the transcriptional level by using a ppk-promoter lacZ fusion reporter system under a variety of stressful conditions. The expression of ppk gene was greatly induced (7-20 fold higher depending on stress or medium) by deficiencies of phosphate, amino acids, or during entry into stationary phase. In this work, evidence was found for two different modes of regulation of ppk transcription in bacteria. In E. coli and S. enterica, ppk expression in response to starvation appears to be dependent on the ppGpp/DksA system and independent of the PhoR/PhoB two-component system under conditions of phosphate starvation. In contrast, increased ppk expression in response to phosphate starvation is dependent on the PhoR/PhoB two-component system in Acinetobacter. sp. ADP1, K. pneumoniae, and V. cholerae. The activity of the ppk promoter is also greatly induced by purine starvation. Purine deficiency seems to be a common stimulus for the induction of ppk expression in both of the above categories of bacteria. However, the induction of ppk transcription by purine starvation seems to be independent of both the ppGpp/DksA system and the PhoR/PhoB two-component system. This result implies the presence of third control system in ppk expression.
Degree
Ph.D.
Advisors
Wanner, Purdue University.
Subject Area
Genetics|Microbiology
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